I been thinking about putting this exhaust on my '13 528i xDrive. If I get the same rear diffuser as the one you got, do you know if it would fit my car? Or would I need a whole new bumper? I'm curious because the stock 528xi bumper is not cut out for dual exhaust; it only has one opening on the left side for the exhaust. Any insight would be appreciated!

the m5 diffuser will only fit your car if you have the m-sport package rear bumper. It won't fit a regular 528 bumper. you can probably source a decent m5 rear bumper on ebay or something